In recent years, noticeably increased trauma-related, sports-related and age-related musculoskeletal injuries have imposed significant medical and socioeconomic burden on patients, families and society.
Conventional orthopedic implants are made from permanent and rigid metals such as stainless steel or titanium (Ti). However, such metals do not have the function of promoting the healing of a broken bone. In addition, permanent metals usually create a stress shielding phenomenon, namely causing bone loss due to the decreased load to the fracture bone, thus impairing the healing, in particular unfavorable to the healing and fixation of an osteoporotic fracture.
Therefore, a material promoting healing through its biodegradability is very much desired clinically. Such material comprises a metal that may gradually degrade in vivo, and induces a proper host response by a released degradation product so as to assist the tissue healing. Such implants, besides efficacious, will be more cost-effective as their use may avoid implant removal surgery and/or related complications, including reducing the risks of re-fracture and infections.
Implants, such as intramedullary nail (IM nail), have long been used for long bone fracture fixation. The conventional implant is a metallic implant which is introduced into a medullary cavity of a bone such as femur, tibia and humerus to stabilize the fracture fragments and restore the anatomical location. In addition, an implant system is also responsible for sharing load and allowing early function of a injured limb. As the implant system is a load-sharing implant, certain stiffness and strength are desired. Therefore, conventional implant systems are made from stainless steel or titanium alloys which are permanent and rigid metals and strong enough to provide mechanical support. It is well known that a biodegradable material degrades over time, and the dimensions and mechanical strength thereof reduce, resulting in an unpredictable fracture fixing effect. Therefore, the biodegradable material may not be suitable for directly manufacturing an orthopedic fixing device for fixation of load-bearing skeletal sites where mechanical loading is imposed to the fixation implant or device.